Air bag units with the basically above-described design belong to the state of the art. With regard to the large number of such safety features being found in some modern vehicles, these safety features have very different shapes and different embodiments in detail. With the increasing number of air bag units installed in a vehicle, these represent a cost factor that is of increasing consequence. With regard to production costs, therefore, efforts are being made to keep the design of air bag systems simple, and in particular also to reduce the number of their components, in order to finally reduce the costs with a lower mounting effort in their assembly. Moreover, simplification measures of this type are desired with regard to the often highly limited space for components in the vehicle. One point to which attention is given here is the fastening of the gas generator in the generator housing. It is essential here to take several marginal conditions into account. Thus, the gas generator must be securely fixed in position in the housing and, with regard to comfort, it must be made sure that vibrations and twistings resulting during the motion of the vehicle do not lead to rattling noises or squeaking noises due to parts rubbing against one another. Furthermore, the generator housing must be reliably sealed in order to prevent the gas that flows out of the generator for inflating the air bag in case of a collision from escaping out of the air bag unit into the environment in an uncontrolled manner. These requirements are to be met, taking into account the tolerances occurring in practice in relation to the dimensional stability of the components.
A special adapter for fixing the gas generator in the generator housing, which is utilized to meet the above-mentioned requirements, is described in EP 0 722 861 B1. The adapter is pushed onto the free axial end of the gas generator and fastened thereto by means of a frictional contact connection. For this, a plurality of axially sloping teeth are arranged on the circumference at the inner wall of the element, which has a hollow cylindrical shape. The adapter, which is open on one side for accommodating the gas generator, is fastened to the housing of the air bag unit by means of a flange arranged on the bottom, sealing this bottom, by means of welding, soldering or gluing together. However, provided that additional sealing measures are not taken in the area of the flange, leakage problems may possibly occur with this solution in view of the frictionally engaged press fit of the gas generator and adapter. Also, it does not appear to be certain that the arrangement guarantees the necessary mechanical stability over the longer term in case of the stress occurring in practice.
An air bag unit, in which an elastic sealing and uncoupling ring is arranged between the gas generator and the air bag housing, is described by DE 197 43 615 A1. However, the solution is devoted, on the surface, to the radial uncoupling of the gas generator against the adjacent housing and the sealing of the generator chamber. A compensation of radial tolerances between the gas generator and the generator chamber is advantageously achieved. In its basic embodiment, the sealing and uncoupling ring abuts against a stop shoulder at the axial end of the generator chamber. A fixing of the gas generator in the axial direction is not achieved in this embodiment by the ring alone. For this purpose, an additional cover is necessary or the ring must be embodied with an additional stopping means according to an embodiment of the solution described in the patent. Consequently, the axial fixing of the gas generator is achieved; however, the geometry of the sealing and uncoupling ring becomes more complicated. Moreover, tolerances of the axial measurements of the gas generator cannot or can hardly be compensated with this solution.